Primary election lesson for GOP: Don't cross the president

That's the lesson many Republicans are drawing from Rep. Mark Sanford's surprise defeat Tuesday in his primary election in South Carolina. The victor, state Rep. Katie Arrington, repeatedly highlighted Sanford's criticism of the president.

The outcome is a cautionary tale for Republicans in Congress who try to work with Trump while also maintaining their independence. One wrong turn – or in Sanford's case, many – and they could face the wrath of a president who is quick to attack detractors as enemies, even in his own party.

"That's ultimately what the race devolved down to, which was, was I Trump enough?" Sanford told reporters on Capitol Hill.

"It's a very tribal environment right now," he said. "Are you for or against Trump?"

He said he hoped his defeat would not dissuade other members from speaking out against Trump. Agreeing to disagree is "a sign of health in our political system."

Sanford is the second incumbent House Republican to lose a primary this year, though the defeat of Rep. Robert Pittenger in North Carolina came despite his staunch support for the president.

Still, Sanford is only the latest casualty in the intra-party conflict that has roiled the GOP in the Trump era. Trump is known to remember slights from lawmakers.

Rep. Martha Roby, for example, was forced into a runoff last week in Alabama after her opponents seized on her own rift with the president. In 2016, after the release of a tape in which candidate Trump bragged about grabbing women, Roby said she wouldn't vote for him for president.